Believing in heaven is a human necessity.
We believe in heaven because human experience renders it necessary for us to hope for a better world beyond this life. Our existence in this world tells us that this life isn't what it must be, thus there has to be something better to look forward to --even if that place can only be found beyond our mortal existence.
We believe in heaven because living through this life also gives us hints of this better world whenever our human faculties of sensory perception and experience shows us beauty as well as make us encounter acts of charity that are motivated by sheer love --we conclude that these things come from a place beyond this realm: God's abode, up there in a place beyond our reach...
...at least for now.